1. Field of the Invention
This invention relates to medical devices and methods. More specifically, the invention relates to a prosthetic disc for intervertebral insertion, such as in the lumbar and cervical spine. The invention also relates to the replacement of zygophyseal joints.
In the event of damage to a lumbar or cervical intervertebral disc, one possible surgical treatment is to replace the damaged disc with an intervertebral disc prosthesis. Several types of intervertebral disc prostheses are currently available. One type available under the trademark LINK.®™ SB Charite (Waldemar Link Gmbh, Hamburg, Germany), includes upper and lower prosthesis plates or shells which engage the adjacent vertebral bodies with a low friction core between the plates. [See EP 1142544A1 and EP 1250898A1] A potential drawback of that design is that the prosthetic device must be inserted from the anterior side of the patient, and this approach can be difficult and may require a vascular surgeon as the prosthetic devices passes near important blood vessels located anterior to the spine. Other currently available intervertebral disc prostheses usually have similar drawbacks, including invasiveness of the surgery and/or surgical skill and complexity.
Another prosthetic approach has been to fuse the vertebrae, for example with transforaminal lumbar interbody fusion (TLIF) surgery or posterior lumbar interbody fusion (PLIF) surgery. Fusion surgery generally requires at least partial removal of one or more facet joints, bone grafting, and support with a fusion cage to stop the motion at that segment. Although the fusion cages can be inserted from the back of the patient, such prostheses generally do not provide a flexible joint at the damaged disc site or other implant site. Thus a potential disadvantage of these fusion approaches is that motion is not restored.
In light of the above, it would be desirable to provide improved prostheses, particularly less invasive surgical prostheses which at least partially restore motion.
2. Description of the Background Art
Published U.S. patent applications 2002/0035400A1 and 2002/0128715A1 describe disc implants which comprise opposing plates with a core between them over which the plates can slide. Other patents related to intervertebral disc prostheses include U.S. Pat. Nos. 4,759,766; 4,863,477; 4,997,432; 5,035,716; 5,071,437; 5,370,697; 5,401,269; 5,507,816; 5,534,030; 5,556,431; 5,674,296; 5,676,702; 5,702,450; 5,824,094; 5,865,846; 5,989,291; 6,001,130; 6,022,376; 6,039,763; 6,139,579; 6,156,067; 6,162,252; 6,315,797; 6,348,071; 6,368,350; 6,416,551; 6,592,624; 6,607,558; 6,706,068 and 6,936,071. Other patent applications related to intervertebral disc prostheses include U.S. Patent Application Publication Nos.: 2003/0009224; 2003/0074076; 2003/0191536; 2003/0208271; 2003/0135277; 2003/0199982; 2001/0016773 and 2003/0100951. Other related patents include WO 01/01893A1, WO 2005/053580, EP 1344507, EP 1344506, EP 1250898, EP 1306064, EP 1344508, EP 1344493, EP 1417940, EP 1142544, and EP 0333990.